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WIDENING HORIZONS OF ENDOSCOPIC SINUS SURGERY
Milind V Kirtane*, Sujata N Muranjan**
*Hon. Professor and Surgeon, Seth G.S. Medical College and KEM Hospital, Parel, Mumbai. Consultant ENT Surgeon, P.D. Hinduja Hospital and Medical Research Center, Mahim, Mumbai **Clinical Associate, Department of ENT, P.D. Hinduja Hospital and Medical Research Center, Mahim, Mumbai.
Endoscopic sinus surgery (ESS) was previously restricted only to tackling pathological conditions in the nose and paranasal sinuses like chronic sinusitis and nasal polyposis. Over the years the scope of ESS has considerably widened with the nasal endoscope now being routinely used to access even the surrounding regions like the orbit, optic nerve, lacrimal sac and the pituitary gland to name a few. Similarly CSF leaks which previously required external craniotomy procedures can now be safely and effectively closed by the endoscopic trans-nasal approach. The chief advantages of the endoscopic route are decreased morbidity and better cosmesis wherein external scars are avoided.Functional endoscopic sinus surgery was first described for the treatment of chronic sinusitis not amenable to conservative treatment. Since then, nasal endoscopy has come a long way, with the endoscope now being routinely used for a wide variety of indications for diseases in the paranasal sinuses and their surrounding regions.
In the nose and the paranasal sinuses, the nasal endoscope is used for tackling pathologies like chronic sinusitis, sino-nasal polyposis, mucocoele excision, cauterization of bleeding points in epistaxis etc. With the help of the endoscope, one can also approach with ease other structures in relation to the paranasal sinuses like the orbit and the optic nerve, the lacrimal sac, the vidian nerve and even the pituitary gland. CSF leaks, which previously required open craniotomy procedures, can now be closed by the endoscopic transnasal approach. The major advantages of the endoscopic route are considerable reduction in the morbidity associated with external surgery and subsequent avoidance of external scars and cosmetic blights.
Endoscopic optic nerve decompression
The optic nerve can be decompressed endoscopically by approaching it through the nose. Familiarity with the anatomy of the spheno-ethmoidal region and the orbital apex is essential before embarking on this procedure.The anterior and the posterior ethmoid cells are first cleared. The optic canal lies lateral to the posterior ethmoidal air cells and supero-lateral to the sphenoid sinus. The bone of the optic canal is then gently removed. Bony fragments or haematoma impinging on the nerve are removed and the nerve is thus decompressed.
There exists some controversy about the role of surgical decompression in traumatic optic neuropathy, since a number of different mechanisms may be responsible for producing the visual loss. (Fig. 1) Pressure by bony spicules, shearing or stretching of nerve fibers, compression by haematoma or oedema, intraneural or perineural haemorrhage, contusion or ischaemia due to thrombus or spasm are the various mechanisms postulated, which may be present alone or in combination, thus casting doubt on the role of surgical decompression. Experience of many workers suggests that best results are obtained when surgery and megadose steroid therapy are judiciously combined. The results of optic nerve decompression for post-traumatic blindness to a large extent depend upon the interval between sustaining the injury and the timing of the surgery. The earlier the decompression is carried out, better are the results. A policy of ‘wait and watch’ would allow a potentially reversible blindness to become irreversible.
Fig 4: Axial CT scan showing left traumatic optic nerve compression. Besides trauma, the optic nerve may need decompression in case of tumours, progressive ischaemic optic neuropathy, osteopetrosis and fibrous dysplasia. In cases of progressive visual loss due to oteopetrosis, once the diagnosis is confirmed, decompression of the optic nerve offers the only chance of recovery or at least preservation of vision. Thanks to the nasal endoscope and a long drill with diamond paste burrs, this decompression can be safely and effectively achieved endonasally. Decreased morbidity, preservation of olfaction, rapid recovery time, more acceptable cosmetic results with no external scars, no risk of injury to the developing teeth in children, and less operative stress in a patient who may have multisystem traumas are only some of the benefits associated with the endoscopic optic nerve decompression.6 Complications as a result of optic nerve decompression could be in the form of haemorrhage, orbital or perineural haematoma formation, post-operative CSF leaks and meningitis.
Orbital decompression
In Grave’s disease, compressive optic neuropathy is a feared, although unusual, complication of thyroid-related orbitopathy. Orbital decompression has to be undertaken in case of optic nerve compression, exposure keratopathy or for cosmesis. Previously this involved an external approach with the removal of the medial orbital wall along with the floor. An intranasal endoscopic approach with the removal of the medial orbital wall and part of the floor has now been advocated as an alternative procedure. [1]After clearance of the ethmoidal air cells, the lamina papyracea is removed. The inferior orbital wall may be removed if required. Further decompression of the orbital contents is achieved by making incisions in the orbital periosteum thereby allowing orbital fat to prolapse.
Orbital complications of sinusitis such as an orbital abscess can also be tackled endoscopically by an experienced surgeon. A complete ethmoidectomy needs to be first undertaken after which the tract of infection can be followed into the orbit.
Endoscopic repair of CSF rhinorrhoea
Cerebro-spinal fluid (CSF) leaks could be secondary to trauma or could be due to a non-traumatic cause. The commonest sites of traumatic leaks are through the cribriform plate and the fovea ethmoidalis (Fig. 2). The frontal sinus as well as the roof and lateral wall of the sphenoid sinus are the other sites (Fig. 3). The leaks can be unilateral or bilateral. As a result of the close proximity of the dura to the field of dissection, CSF rhinorrhoea is one of the dreaded complications of endoscopic sinus surgery. The incidence and risk of meningitis justify treatment in all cases of cerebrospinal fluid rhinorrhoea. [7] The surgical management of CSF rhinorrhoea has been modified these last years due to the improvement of endoscopic sinus surgery techniques, allowing the treatment of selective dural tears by the endonasal route. [2] The excellent illumination and clear vision offered by the nasal endoscope makes it possible for leaks through the anterior skull base to be repaired with ease by the endonasal route. All such sites except frontal sinus leaks can be approached trans-nasally with the help of the nasal endoscope. It is essential to confirm the exact site of the leak preoperatively by CT scan with metrizimide contrast or MR scanning. The basic principle of endoscopic CSF rhinorrhoea closure involves identification of the site of leak, making the surrounding area raw, plugging the defect with fat or muscle and covering it with fascia. Materials that can be used are temporalis fascia or fascia lata, mucoperichondrium of the septum or the turbinates or lyophilized dura. In very large defects, a piece of autograft cartilage can be used to strengthen the defect. Postoperative lumbar drainage may be done to reduce the CSF pressure.
Fig 2 : CSF leak through a break in the right cribriform plate.
Fig 3 : CSF leak from lateral wall of left sphenoid sinus with fluid in the sinus. When the defects in the anterior skull base are accessible to the endoscope, an endoscopic approach should be considered as the preferred method in all the cases. [5] It is an excellent substitute for the transcranial procedure, the procedure being quick, with negligible morbidity and good results, and a major surgery like a craniotomy can be avoided. In case of failure, it does not in anyway interfere if a transcranial intervention needs to be undertaken at a later date.
Endoscopic management of mucocoeles
Mucocoeles form as a result of obstruction of the paranasal sinus ostia wherein the mucus and secretions accumulate within the cavity of the sinus leading to considerable expansion of the sinus. Preservation of the lining mucosa of the mucocoele by marsupialization has been advocated by many authors. [10] Since functional endoscopic sinus surgery provides a minimally invasive approach under local anaesthesia, it affords the potential for dramatically reducing the morbidity involved in treating mucocoeles by decreasing blood loss and avoiding external incisions. It also allows direct visualization of the mucocoele cavity and early detection of recurrences. To visualize a frontal sinus mucocoele, the anterior ethmoidal cells are first cleared upto the ground lamella. The anterior skull base is then visualized and the frontal recess area identified. The inferior aspect of the mucocoele can be typically visualized bulging into the frontal recess area. An incision is made over the bulge and the secretions are aspirated. The opening is widened so that the mucocoele is adequately marsupialized into the nose. Care is taken to preserve the mucosa of the frontal recess area to prevent adhesions, scarring and subsequent recurrences. Ethmoid sinus, sphenoid sinus and maxillary sinus mucocoeles can be similarly tackled by exposing the bulging wall of the mucocoele and then marsupializing it into the nose (Fig. 4). Mucocoeles occurring in the lateral part of the frontal sinus cannot be approached endoscopically and require the more traditional external approach. The mucocoele or pyocoeles must always be widely marsupialized to avoid a recurrence. Close follow up of the patient is a must. Scar bands, polyps and crusts must be meticulously removed to keep the mucocoele opening patent to prevent re-stenosis and subsequent recurrences.
Fig 4: Coronal CT scan showing a large right ethmoid mucoele involving the orbit. Endoscopic Dacryocystorhinostomy
Conventional dacryocystorhinostomy (DCR) usually involves extensive removal of bone at the lacrimal fossa and hence risks disruption of the lacrimal pump mechanism. The lacrimal sac can alternatively be approached with ease through the nose with the help of the nasal endoscope. This is a more physiological approach for naso-lacrimal blockage whereby only the inferior portion of the lacrimal sac and the adjacent duct are marsupialized into the nose. [9]
In patients with apparent dacryocystitis (Fig. 5), blockage of the nasolacrimal duct may be inferred by doing sac syringing. If the irrigation fluid flows out through the superior lacrimal punctum, it indicates that the canaliculi are patent, and the patient would benefit from an endoscopic DCR. However if there is a reflux of fluid through the lower punctum itself, it signifies a canalicular block, in which case a DCR is contraindicated. The diagnosis of chronic dacryocystitis can be confirmed with the help of a dacryocystogram wherein dye is seen in the sac with an obstructed naso-lacrimal duct through which the dye fails to flow.
Fig 5 : Clinical photograph showing right side lacrimal sac pyocoele. The lacrimal bone and the frontal process of the maxilla form the anterior part of the lateral nasal wall. The mucosa of the lateral nasal wall anterior to the uncinate process is removed. The underlying bone is then exposed. With the help of a bone punch forceps, this bone is removed so that the sac can be visualized. Following exposure, the sac is then incised and the pus allowed to drain out. The opening in the sac is then widened. The patency can also be confirmed by injecting methylene blue dye through the lacrimal punctum and watching it trickle into the nose. A silicon stent is kept for a period of 4-6 weeks to prevent re-stenosis.
The endoscopic approach is safe, quick, and far less traumatic, and yet as efficacious as the conventional approach, avoiding the need for a skin incision and disruption of the medial canthal structures. [ 3]
Endoscopic Hypophysectomy
Transseptal trans-sphenoidal surgery of pituitary tumours is a well-established surgical technique. The sublabial and the open rhinoplasty approaches are most commonly used. In both cases, the surgical avenue is along the entire length of the nasal septum, by performing a submucous resection of the nasal septum. [8] The nasal endoscope has made it possible to access the pituitary gland through the sphenoid sinus in order to excise tumours like microadenomas and for purpose of obtaining biopsies. By this method, the need for performing an SMR is obviated.
Under endoscopic guidance, the anterior wall of the sphenoid sinus is opened. After adequate widening of the opening, the sphenoid sinus is entered The mucosa of the sinus is then removed to avoid any intra-operative bleeding in an effort to have a clear field. The bulge of the pituitary gland is visualized, following which the bone over the anterior wall of the sella is thinned out and subsequently removed. An opening 8-10 mm wide is enough for a good exposure of the gland. The dura is then visualized and incised in a cruciate manner thus exposing the pituitary gland. The endonasal trans-septal approach is more anatomical and less traumatic than the rhinoseptal sublabial route.[4]
Choanal atresia
Recently the nasal endoscope is also being used to diagnose and perform surgeries for choanal atresia. Bony atretic plates can be burred safely under vision to create large openings that will remain patent. However one must remember that stenting will be required in any case.
Excision of Rhinosporidiosis
Rhinosporidiosis is a granulomatous lesion caused by a fungus Rhinosporidium Seeberi. The lesions commonly occur in the nasal cavity and spread to the paranasal sinuses, pharynx, larynx, lacrimal sac and conjunctiva. The lesion is polypoidal, highly vascular with a whitish speckled appearance due to presence of sporangia.
Traditionally when these lesions were excised transnasally, implantation of spores in the adjacent raw areas created by blind surgical removal, often led to recurrences, which necessitated multiple surgical procedures. This can now be overcome with the help of the nasal endoscope which allows identification of the base / pedicle of the lesion which is then cauterized thus enabling complete atraumatic excision. Bleeding during excision and subsequent recurrences can thus be avoided. Lesions restricted to the nasal cavity can be excised with ease under endoscopic guidance.
Foreign body removal
The nasal endoscope is a valuable tool for diagnosis and removal of foreign bodies in the nasal cavity and maxillary sinus. Foreign bodies embedded in the maxillary sinus can be removed by approaching the maxillary antrum either through its natural ostium in the middle meatus or by the canine fossa puncture technique. (Fig. 6)
Fig 6 : X-ray PNS water's view showing a foreign body in the right maxillary sinus. Tumours
Though the use of the endoscope in the treatment of benign and malignant tumours is quite controversial, tumours can be diagnosed earlier and difficult anatomical areas previously unreachable, can now be biopsied, thus avoiding the morbidity of an open procedure. Benign lesions like inverted papillomas, which are restricted to the nasal cavity and medial wall of the maxillary sinus (Fig. 7), can be excised completely with the help of the nasal endoscope. Pituitary cysts, retention cysts and fibrous dysplasia are the other benign conditions, which can also be tackled endoscopically. Nasopharyngeal lesions, clivus tumours and tumours of the sphenoid sinus can be easily biopsied under endoscopic guidance. Besides initial diagnosis and biopsy, endoscopy is extremely helpful in follow up of nasal and paranasal sinus lesions. Postresection diagnostic follow-up allowing early localization of recurrence is now possible with the help of the nasal endoscope.
Fig 7: Coronal CT scan demonstrating a right nasal inverted papilloma. All the above mentioned surgeries may be safely carried out with minimum morbidity provided the operating surgeon has a sound knowledge of the anatomy of the nose, the paranasal sinuses and the surrounding structures. It is therefore essential for the operating surgeon to familiarize himself with the anatomical landmarks prior to embarking on any procedure. Armed with this knowledge, it is then possible to use the nasal endoscope to its fullest advantage.
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- Yaniv E, Rappaport ZH. Endoscopic transseptal transsphenoidal surgery for pituitary tumors. Neurosurgery May 1997; 40(5) : 944-6.
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- Josephson J.S., Alfredo Herrara V.: Mucocoeles of the Paranasal Sinuses- Endoscopic Diagnosis and Treatment, Advanced Endoscopic Sinus Surgery, Mosby Year Book Inc., 1st Edition, 1995; 51-59.
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